[gpfsug-discuss] mmchfs -k nfs4 impacts?

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Mon Aug 29 22:05:47 BST 2022

On 29/08/2022 18:52, Losen, Stephen C (scl) wrote:

> Hi,
> We want to export  SMB shares via Spectrum Scale CES nodes. The 
> filesystem has ACL style set to “all” and we must set it to nfs4 with 
> mmchfs -k nfs4 . The filesystem currently has millions of files with 
> POSIX ACLs. Will this mmchfs command result in any performance impact, 
> such as a major rewrite of metadata? Thanks.

The operation will complete very quickly. The bigger risk is that your 
existing ACL's will go "puff".

As I understand it GPFS stores each different ACL only once and then it 
points each file to the ACL. When you change the ACL type they get nuked 
from recollection but it is a decade now since I played around with 
that. I stick to NFSv4 ACL's since then because well POSIX ACL's are a 
bit naff frankly.

I personally would have thought "-k samba" would have been preferable 
for your use case mine you ;-)


Jonathan A. Buzzard                         Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG

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